Electric switch-board



(No Model.) 2 Sheets-Sheet 1.

I. H. FARNHAM. ELEGTRIG SWITCH BOARD. I No. 394,964. Patented Dec. 25,1888.

i I L W'fiaesses 17506722507,

NY PETERS. Pholu-LllhoguphcL Waslunglon. u c.

2 Sheets-Sheet 2.

I. H. PARNHAMf ELECTRIC SWITCH BOARD.

(No Model.)

Patented Dec. 25, 1888.

N. PETERS Phclo-Lilhognpbcr. Waslxinglom n. c

UNITED STATES PATENT ElFlQE.

ISAIAH H. FARNHAM, OF MALDEN, ASSIGNOR TO THE NElV ENGLAND T ELE- PHONEAND TELEGRAPH COMPANY, OF BOSTON, MASSACHUSETTS.

ELECTRIC SWlTCt-HBUARD.

SPECIFICATION forming part of Letters Patent No. 394,964, dated December25, 1888.

Application filed September 8, 1888. Serial No. 284,912. (X modeld Toall whom it may concern.-

Be it known that I, ISAIAH H. FARNHAM, residing at Malden, in the countyof Middlesex and State of Massachusetts, have invented certainImprovements in Electrical Switch- Boards, of which the following is aspcciflca tion.

l l l l This invention relates to electrical switchboards, and moreparticularly to means for contacts from dust and lint or otherobstructions which have a tendency to accumulate within the crevices oroperating-apertures of such appliances and which interferes with theirproper and successful operation.

It comprises the application to any form of switch-board of means forcausing a continuous or periodic flow of air outwardly through theseveral springjacks thereof, and since the best results are attained andthat the greatest number can be operated in a single switch-board wheneach line passes through permanent spring-jack contacts and when theconnection between any two lines or between any one line and thecentral-station apparatus effected by means of flexible conductors. Suchswitch-lmards are therefore I now universallypreferred to switch-boardsof To protecting their spring-jacks and spring-jack the spring-jacks ofhorizontal switch-boards 5 are (inasmuch as they are verticallymounted l2 5 and other causes it especially comprises the application of suchmeansto switch-boards ot such character.

It contemplates also the casing up of the rear or lower side of theswitch-board in an 0 approximately air-tight manner, so that acomparatively feeble air-pressure may be altogether exerted in theproper directionviz., outwardly through the swing-jacks; and itconsists, furthermore, also in providing appa- 3 5 ratus-such as afan-driven by steam or other power, a pipe carrying cold air rarefied intransit by proximity to a hot-air pipe, a steam-pipe or otherwise or bypedal-operated bellows, also in heating the said air so rarefied by thesame means, and, finally, in pro viding and combining with the saidapparatus for increasing the air-pressure behind the switch-boardsuitable cleansing devices through which the said air must pass on itsway to the switch-board, whereby all impurities may be arrested andprevented from pass ing into the switchboard casing.

The switclrboards employed in large telephone-exchanges must necessarilybe of suf 5o ficient capacity to accommodate a very great number oflines, and it has been found that that class wherein permanent verticaland transverse conducting-bars adapted to be connected by metallic pinsat their intersections are employed. Moreover, it is sometimes foundadvantageous to construct horizontal face switch-boards such asindicated in the drawings, because by employing these more operators areenabled to reach the same number of spring-jacks, and therefore whenmultiple switch-boards are required a less frequent multiplication isnecessary with the horizontal or flat board than with boards having asusual a vertical face, and consequently the flat board tends to materialeconomy in construction. In both forms it has been found that dust anddetritus tend to accumulate within the spring-jacks, although the saidtendency is obviously much more pronounced and injurious inthehorizontal form of switchboard than in the other. The presence ofsuch extraneous matters seriously impairs the efficiency of the contactsand sometimes interposes so high a resistance between the restingcontacts as actually to open the main circuit.

In the drawings which illustrate and form a part of thisSPQClflCtll'lOll, Figure 1 is a perspective view of a switch board casedup round the rear part of the spring-jacks and combined in accordancewith this invention with means for increasing the air-pressure in theinterior of such casing, and thus for producing a gentle circulationoutwardly through the spring-jacks. Fig. 2 a view of a cleansing-screensuitable for employment in connection with the apparatus. Fig. 3 is avertical transverse cross-section of a horizontal switch-board, takenthrough a line of springjacks and showing the main air-pipe, also incross-section. Fig. l is a detail of a modification indicating theformation of an air-cur rent due to rarefaction by means of the pro:;=

imity of a steam-pipe. Fig. 0 shows an airpipe in which the air isheated and rarefied by leading the pipe through a chimney-flue; and Fig.6 shows a switch-board having its air currents established, whendesired, by means of pedally-operated bellows under control of theoperator.

In Figs. 1, 3, and 6, a is a switch-board of that class which may betermed horizontal switch-boards. The said switch-board is or may bemounted upon the floor of the operating-room, as shown, or upon araisedplatform adapted for the purpose, and the under or back part of theboard is cased upmoderately air-tight, so that all of the rear ends ofthe plug-sockets or spring-jacks open into an inclosed space, as clearlyindicated in Fig. 3. The rear wall of this air-tight casing may be closeto the floor, or, if desired, at a higher point from side wall to sidewall. This isnot material.

The several series of spring-jacksj may, as usual be constructed inindependentsections or panels, as .in Fig. 1, where four of such springjack containing panels are shown placed side by side at the right-handend of the switch-board, the other panel places, 3, being in thedrawings unfilled. The tirstside space, 2, may be filled up withconnecting plugs g, each constituting the end of a flexible conductor,and each capable of being raised in a manner well understood andinserted in any of the spring-jacks for the purpose of making orchanging an electrical connection. Still nearer the edge of theswitchboard face, upon the longitudinal space 1, and this at both sides,may be ranged the calling keys or buttons 7;.

The call-receiving annunciators .2 may also be arranged inpanel-sections i on both sides of a raised box, B, which extendslongitudinally from one end to the other of the switch board, beingsupported thereover upon hollow pillars or columns 5, through which, orotherwise, their connecting-wires may be led.

In order to keep dust and such matters entirely out and to do thiswithout any alteration or attachment to the jacks,I provide means forslightly raising the air-pressure within the case or back of theswitchboard, and this increase of pressure causes an outward circulationof air through the jacks or plug-sockets, and, in fact, through anyopening, aperture, or crack which may be in or about the board, asindicated by the arrows, Figs. 1 and 3. In Fig. 1 is shown suitableapparatus for accomplishing this. Afan-blast, F,

, driven, as indicated, by steam or other power, is

conveniently placed in or near the switchingroom, or where desired, andsupplies the required air-pressure and circulation .by means of thepipes 19 and p, the air passing through the pipe 19 being preferablyforced through a cleansing-box, 6, in which any desired number ofscreens or strainers, 7, maybe placed for the purpose of preventing dustor obj ectionable matter from being carried into the casing with theair. These screens, 7, may be made of such a construction that they canbe easily introduced or withdrawn from the box (3, and the severalslides will preferably be made with different grades of mesh, fromfairly close cloth to wire-netting. This box (3 is placed intermediateiybetween the fan and the switch-board, and the pipe 1), after leaving thesaid cleansing-box, passes to the switch-board, and, entering theinclosed space thereof, may be extended longitudinally therein, as shownin dotted lines in Fig. 1.,and may be perforated at as many points asdesired, as indicated in crosssection in Fig. 3, for the distribution ofthe fresh-air supply.

The adoption of this invention will totally prevent the deposition ofdust, because the air under a determinate pressure is constantly incirculation, and because that circulation is with respect to thespring-jacks at all times outward.

Other apparatus may be substituted for the fan-blast without departingfrom the spirit of my invention.

Referring, for example, to Fig. i, the supply of air may be taken fromthe outside of the building by means of a pipe, (1, extending throughthe wall in, the said pipe being provided at its mouth with asuitablestrainer, e. The pipe (Z connects with or continues as the tube b,through which a steam, hot-air, or hotwater pipe, .9, passes, this beingmainly used for heating purposes. The inclosing draft pipe I) is ofcourse sealed at the points g and c, where the steampipe enters andleaves it, and from the pipe I) the pipe to the switchboard is led. Thepipe p may be, as with the former apparatus, led through the screenbox6. In the adoption of this apparatus a circulation would be createdbythe rarefaction consequent upon the heating derived from the steam-pipe,and air would consequently pass readily through and increase thepressure within the closed snitch-board casing, relieving itself, ofcourse, through the spring- ;jack, in the manner already described.

If desired, of course, the circulating air may be also in this waywarmed on its way to the board, and during the summer the air may byequally simple means be cooled. The air-pipe may, for example, be ledthrough a trough in which ice may be placed, or into which water iscaused to flow or drip over the said air-pipe; but in any case the airwhich is forced into the back of the switch-board for increasing thepressure should always be taken from out of doors, and will then greatlyaid in giving good ventilation to the usually crowded room; or, again,the induction-pipe 1) may 011 its way to the switch boa-rd, as in Fig.5, be led through the flue f of a chimney, C, through which the heatedproducts of combustion are passing, and the rarefaction and consequentcirculation may in this way be produced.

If none of the modes and apparatus which I have described be in anyindividual case convenient, recourse may be had, as shown in.

Fig. 6, to a series of bellows to be actuated whenever desired by thefoot of the operator. In the figure, a is the switchboard; R, a pair ofbellows, of which as many as may be rendered necessary by the size ofthe switchboard may be provided. p is the main airpipe, 9 thebellows-pedals projecting from the switch-casings, and S thepipe-nozzles projecting from the several pairs of bellows into thecasing.

It may not in every case be necessary that the pressure-producing orair-circulating apparatus shall at all times be in operation, sinceperiodic operation, if of regular and frequent occurrence, will meet thedesired end.

I am well aware that dust-guards have heretoforebeenpatented inconnection with switchboards; but, as will have been seen, I propose toattack the evil from another direction and to keep the dust entirely outof the jacks, and that without complication in or addition to theconstruction of the said jacks.

Of course I am not restricted to any particular length of switch-board,and section after section provided with means for circulating airthrough the spring-jacks outwardly can readily be added end to end.

I claim as my invention 1. An electric switch-board having springjacksor plug-sockets on .its face, and hay-. ing an air-tight casing at itsrear inclosing the rear end of the said jacks or sockets, com bined,substantially as described, withmeans for increasing the air-pressurewithin the said i casing and for maintaining a circulation of 3 airthrough the said spring-jacks in an outswitchboard casing may beincreased and circulation through the spring-jzu-ks in an out warddirection maintained.

t. In combination with a switch-board haw ing a horizontaloperating-face,with its springjack orifices pointing upward, andprovided with an approximately air-tight casing at its rear side, withinwhich the inner ends of its spring-jacks are inclosed, an air-pipeleading into the said 'incloscd chamber, and a fanblast or itsequivalent for forcing air under suitable pressure through the said pipeinto the said chamber, and thus to establish circulation oi' twardlythrough the spring-jacks, as

f and for the purposes described.

An electric switch-board having a flat and horizontal operating-face andspringjacks or plug-sockets yertically mounted therein, with theirorifices open in an upward direction, the said switch-board beingconstructed with an approximately air-tight casing inclosing the innerends of the said springjacks, combined with an air-pipe leading from theopen air into the said inclosed chamber, a fan or otherpressureproducing device for forcing the air through said pipe into saidswitch-board casing, and a cleansing-box fitted with strainers orscreens to arrest and retain impurities included in said air-pipebetween the said pressure-producin g device and the switch-boardchamber, substantially as described, and for the purposes specified.

In testimony whereof I have signed my name to this specification, in thepresence of two subscribing witnesses, this 28th day of August, 1888.

ISAIAH H. FARNHAM.

lYitnesses: I

GEO. WILLIs PIERCE, J OHN F. )IARTIN.

